Preheat broiler to high or oven to 400F.
Place a large pot of water over high heat and bring it up to a boil to cook the pasta. Once at a boil, add pasta and salt the water, cook to just shy of al dente.
Heat a large pot over medium heat with EVOO and butter. When butter melts, add the onions, garlic, salt and pepper, and cook until softened, about 5 minutes, stir in paprika. Add the flour and cook a minute more. Whisk in milk and hot sauce, and bring up to a bubble, thicken a minute or 2. Turn off the heat, and stir in half of the cheese in a figure-eight motion until melted.
When the pasta is done, drain it well and add it to the pot with the cheese sauce. Toss to combine. Fold in the drained pimentos, pour into into baking dish and top with the remaining cheese, brown under the broiler.
Garnish with the chopped parsley and a generous sprinkle of sweet paprika. Serve with Honey-Mustard Dressed Green Bean Salad alongside.